To insert accent marks, tildes, inverted question and exclamation marks in Word, use the following keystrokes:
 

For Word 95 & 98

for accent marks,  [ctrl + ] then the letter
for ~ ,  [shft + ctrl +~] then n
for ¿,   [shft + ctrl + alt + ?]
for ¡,  [shft + ctrl + alt + !]

For Word 2000

for accent marks,  and then the letter
for ~, [shft + ctrl +~] then n
for ¿, [ctrl + alt + ?]
for ¡, [ctrl + alt + !]
 
 
Here's a list of some:
"Alt" + 130 = é
"Alt" + 132 = ä
"Alt" + 137 = ë
"Alt" + 139 = ï
"Alt" + 142 = Ä
"Alt" + 144 = É
"Alt" + 148 = ö
"Alt" + 152 = ÿ
"Alt" + 153 = Ö
"Alt" + 160 = á
"Alt" + 161 = í
"Alt" + 162 = ó
"Alt" + 163 = ú
"Alt" + 164 = ñ
"Alt" + 165 = Ñ
"Alt" + 168 = ¿
"Alt" + 173 = ¡